Views:9 Author:Site Editor Publish Time: 2019-07-02 Origin:Site
Cork is commonly known as cork, cork. The outer product of a very well developed layer of plant cork, the surface protective tissue of the thickened stems and roots. Cork for general commercial use is harvested primarily from the bark of cork oak. Oak trees mainly live in the west coast of the Mediterranean basin, mainly distributed in seven countries: Portugal, Spain, France, Italy, Mexico, Algeria and Tunisia. Our qinling mountains also have a small yield.
The growth of cork forest not only has the requirement of climatic condition, more requirement soil has content of certain nitrogen, be rich in potassium, PH value achieves 5/6. The ideal growing environment is 100 to 300 meters above sea level, with annual precipitation of 400 to 800 millimeters. Perennial temperature not less than 5 degrees, affected by the Atlantic wind. So, Portuguese good natural environment, it is the cork kingdom with world recognition, the output of cork and its products and quality all top the world. Portugal has cork oak forests of 660,000 hectares, accounting for 30% of the total area of European cork oak, producing 50% of cork raw materials and supplying 75% of the world's raw materials.
Cork is composed of flat cells. Often contain colophony and tannin compound inside cell lumen, air is full of inside the cell, consequently cork often has color, quality of a material is light soft, be full of flexibility, impervious to water, suffer the action of chemical medicaments not easily, and it is the bad conductor of report, heat harmony. Composed of dead cells in a 14-sided body, arranged radially between hexagonal prisms. Typical cells are 30 microns in diameter and 1 to 2 microns in thickness. No ducts between cells. The space between the two adjacent cells consists of five layers, two of which are fibrous, followed by two layers of cork, and in the middle by a lignified layer, with more than 40 million cells per cubic centimeter. The still air inside its cell cavity accounts for 70% of unit volume, the specific gravity is 0.24, so cork is light material, between adjacent cells by resin caulking, make each cell become impermeable, impermeable fluid sealing unit. It is because the soft without special cell structure and chemical composition, so that it has a good open air cushion elasticity, shock absorption function, and excellent sound absorption, insulation pad, corrosion resistance, moistureproof, wear resistance, fire resistance and other properties.
Cork has very good flexibility, sealing, heat insulation, sound insulation, electrical insulation and friction resistance, plus non-toxic, tasteless, small proportion, soft feel, not easy to catch fire and other advantages, so far still no artificial products comparable to its comparable. In terms of chemical properties, the ester mixture formed by several hydroxyl fatty acids and phenolic acids is the characteristic component of cork, collectively referred to as cork grease. This kind of material is resistant to decay and chemical erosion, so in addition to concentrated nitric acid, concentrated sulfuric acid, chlorine, iodine and other corrosive effects, water, grease, gasoline, organic acids, salts, esters and other chemical effects. USES are very wide, such as bottle stopper, refrigeration equipment insulation layer, life buoy, soundproof board, etc.
Cork products: (1) natural cork products. After cooking, softening, drying, directly cut, stamping, rotary cutting and other methods into finished products such as plug, pad, crafts and so on.
(2) baked cork products. The remaining material of natural cork products is crushed and then compressed into shape. It is baked in the oven of 260 ~ 316℃ for 1 ~ 1.5 hours. It can also be made by superheated steam heating.
(3) cement cork products. Cork fine particles and powder, adhesive (such as resin, rubber) after mixing into cementing cork products, such as flooring veneer, sound insulation board, heat insulation board, widely used in aerospace, ships, machinery, construction and other aspects.
(4)cork rubber products. With cork powder as raw material, rubber content about 70% made. Has the compressibility of cork and the elasticity of rubber. Mainly used as engine and other excellent low, medium pressure static sealing materials, also can be used as seismic, sound insulation, friction materials.